The present invention relates generally to the field of photovoltaic cells, also commonly known as solar cells. More particularly, it relates to structures referred to as solar panels, by means of which a plurality of solar cells are maintained in substantially fixed relationship with respect to each other and are protected from ambient conditions while being exposed in light-receiving position.
As a general procedure, solar panels are usually manufactured first by soldering or otherwise joining individual solar cells to form a strip of cells that are connected to each other in series or in parallel. The strip of cells is adhered within a tray having an open face, generally by an adhesive material so that, after curing of the adhesive, the cells are maintained in fixed position within the tray. Adhesive material is often used an an encapsulant for the cells, i.e., it completely surrounds the cells and serves not only to keep the strip of cells in position to receive light so that the cells do not shift when subjected to external jarring or even when the panel is moved from one location to another, but also protects the cells from rain, snow and other ambient conditions that will detract from the performance of the cells. When a strip of cells in a panel is to be encapsulated, the encapsulant selected is one that is transparent and has desirable light-transmitting properties; it provides minimal obstruction to the passage of light of those wavelengths for the reception of which the cells have been designed. Also, the encapsulant will have optimal weathering characteristics, even if a further protective cover, e.g., a sheet of glass, is provided to cover the open face of the tray.
Solar panels should have as high a life expectancy as possible. As stated in commonly assigned U.S. Pat. No. 4,057,439 to Dr. Joseph Lindmayer, the disclosure of which is incorporated by reference herein for use where requisite, the life of solar panels should be ten, preferably twenty years. While properly protected photovoltaic cells, having no moving parts, have an indefinite life span, solar panels that house the cells present a greater problem in terms of life expectancy. When delamination occurs, or one of the basic components of the panel fails, the entire panel can become inoperative although all, or almost all of the solar cells within the panel are in operative condition. The Lindmayer patent is directed to a solar panel in which a silicone resin is utilized as an encapsulant.
While the Lindmayer patent was directed primarily to overcoming the problem of delamination of the cured encapsulant layer from the panel, as would be expected, there are still many other problems extant in the manufacture and use of solar panels, both from ambient conditions and in economies of panel making. Thus, one problem that is extant is achieving perfect alignment of cells where more than one strip of cells is housed within a single solar panel. Since the cells of the strip or string are all joined one to the other by soldering, the longer the string the more the possiblility of deviation from a flat, aligned strip, as the strip will tend to float in its encapsulant before the encapsulant has been cured from a liquid to a solid state. Also, air bubbles can become trapped beneath cells in the liquid encapsulant, leading to oxidation and deterioration of photovoltaic characteristics in the cells. Finally the need to solder adjoining solar cells together represents an added expense, for the portions of the cells to be joined must be coated with a relatively expensive, solderable material before such soldering can take place.